1. Field of the Invention
This invention relates to the cutting of vegetation, and more particularly relates to a rotary-type lawnmower employing cutting elements of flexible, non-metallic polymeric material.
2. Description of the Prior Art
In the cutting of vegetation such as lawns and other green spaces, the motorized rotary lawnmower employing a metal blade has been found to be very useful and highly acceptable to both commercial and homeowner users. In this lawnmower, a metal blade of between 18 and 36 inches is rotated about a vertical axis, with a peripheral tip speed of several thousand feet per minute. The blade, weighing from about three to seven pounds, represents a tremendous amount of force as kinetic energy. This vast force is advantageous in providing a relatively uniform rotational speed for cutting vegetation. However, the disadvantages of a moving heavy metal blade are most apparent. The blade has inflicted injuries to persons in the range of nearly a hundred thousand reported accidents per year. For example, the metal blade at operative rotary speeds, upon contact with a human part such as a finger or foot, results usually in a severe injury.
Various governmental agencies and industrial organizations have suggested using guards, dead-man controls, and other safety features on the rotary lawnmower in an attempt to reduce the magnitude, severity and number of injuries inflicted by the rotary metal blade. Unfortunately, the ultimate problem with the rotary-bladed lawnmower is in the rotary blade, which provides not only the desired cutting action for vegetation removal, but also the hazardous instrumentality for injury to humans.
Examination of the cutting action involved with the rotary metal blade shows that only its tip actually cuts the vegetation. However, the remainder of the blade moves at high angular velocities and can inflict as much injury to objects and to humans as the cutting tip. A small metal blade could be mounted peripherally upon a disc so that a safer rotary lawnmower would be obtained while preserving the desired cutting action of the cutting tip. Usually, the small metal blade must be pivotally mounted to the rotating disc. As a result of wear, accidents or misuse, the blade can escape from the disc at operative speeds, becoming a most destructive projectile.
The hazards with metal blades in rotary-type edgers and trimmers have been avoided by apparatus defined in U.S. Pat. Nos. 3,708,967; 3,826,068; and 3,859,776. In these patents, there are described apparatus employing a rotating head carrying one or more extending flexible non-metallic cutting members which are adapted for cutting and trimming vegetation and the like. The cutting members are preferably Nylon.RTM. lines within certain relationships of diameter, length and tip peripheral speed. Apparatus constructed according to these patents have found immediate commercial success and are rapidly supplanting the use of metal-bladed trimmers and edgers, because of (1) the great safety in operation provided by this equipment; and (2) the better vegetation-cutting performances in edging and trimming of this equipment.
A lawnmower constructed in accordance with the operating criteria of these patents has been referred to as a related application to the present invention now U.S. Pat. No. 4,112,653. In this related case, the lawnmower employs one or more flexible non-metallic cutting members such as cord-like Nylon.RTM. line. The line is mounted upon a planar-type disc member which is rotated by an internal combustion or electric motor. The cutting members are of short length and have peripheral tip speeds of between about 14,000 and about 30,000 feet per minute. Lawnmowers constructed according to this principle have been demonstrated as cutting vegetation as well as does the rotary metal-bladed lawnmower.
The present invention is a rotary lawnmower which improves upon the structure of the lawnmower in the related case. In particular, the present lawnmower is constructed so as to be completely safe to the user. In no event can the user encounter the rotating elements of this novel lawnmower and be injured as if struck by a rotating metal blade. The present lawnmower employs a cutting pin formed into a novel structure from a flexible and non-metallic polymeric material. This cutting pin is easily inserted and removed from a rotatable head member and performs cutting operations substantially equal to metal-bladed rotary lawnmowers but without their attendant serious hazards.